I would also suggest booting into live media, be it in the form of USB or CD/DVD to enter a working desktop environment, although I have not had any experience with Boot Info Script and would suggest that, if you have problems with it, you should give "Boot repair" a go. Once in a working desktop environment and connected to the internet, run these commands to install "Boot Reapir":
sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
And then this one:
sudo apt-get install -y boot-repair && boot-repair
Once this has completed, if you feel confident, have a go with the software and see if it can fix your issue.
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EDIT: After re-reading your question it seems that your issue is with the Windows side of things. I have had the same issue before and found a solution online somewhere, although I cannot remember it, I do remember that you can access a cmd using the Windows 7 installation disc and visiting the repair option. A google search might come up with a solution using the command prompt.